Crossing the phantom divide: theoretical implications and observational status

@article{Nesseris2006CrossingTP,
  title={Crossing the phantom divide: theoretical implications and observational status},
  author={Savvas Nesseris and Leandros Perivolaropoulos},
  journal={Journal of Cosmology and Astroparticle Physics},
  year={2006},
  volume={2007},
  pages={018-018}
}
If the dark energy equation of state parameter w(z) crosses the phantom divide line w = −1 (or equivalently if the expression d(H2(z))/dz−3Ω0mH02(1+z)2 changes sign) at recent redshifts, then there are two possible cosmological implications. Either the dark energy consists of multiple components with at least one non-canonical phantom component or general relativity needs to be extended to a more general theory on cosmological scales. The former possibility requires the existence of a phantom… 

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